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authorYinghai Lu <Yinghai.Lu@Sun.COM>2007-07-15 23:37:59 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-16 09:05:35 -0700
commit18a8bd949d6adb311ea816125ff65050df1f3f6e (patch)
tree4365db908430747a5c08cacdb4354577b7bfead7 /Documentation
parentb1c931e39327ef121797927d4b3198d370e75b9b (diff)
serial: convert early_uart to earlycon for 8250
Beacuse SERIAL_PORT_DFNS is removed from include/asm-i386/serial.h and include/asm-x86_64/serial.h. the serial8250_ports need to be probed late in serial initializing stage. the console_init=>serial8250_console_init=> register_console=>serial8250_console_setup will return -ENDEV, and console ttyS0 can not be enabled at that time. need to wait till uart_add_one_port in drivers/serial/serial_core.c to call register_console to get console ttyS0. that is too late. Make early_uart to use early_param, so uart console can be used earlier. Make it to be bootconsole with CON_BOOT flag, so can use console handover feature. and it will switch to corresponding normal serial console automatically. new command line will be: console=uart8250,io,0x3f8,9600n8 console=uart8250,mmio,0xff5e0000,115200n8 or earlycon=uart8250,io,0x3f8,9600n8 earlycon=uart8250,mmio,0xff5e0000,115200n8 it will print in very early stage: Early serial console at I/O port 0x3f8 (options '9600n8') console [uart0] enabled later for console it will print: console handover: boot [uart0] -> real [ttyS0] Signed-off-by: <yinghai.lu@sun.com> Cc: Andi Kleen <ak@suse.de> Cc: Bjorn Helgaas <bjorn.helgaas@hp.com> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Gerd Hoffmann <kraxel@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/kernel-parameters.txt11
1 files changed, 9 insertions, 2 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4d880b3d1f35..62aab585d9d7 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -462,13 +462,20 @@ and is between 256 and 4096 characters. It is defined in the file
Documentation/networking/netconsole.txt for an
alternative.
- uart,io,<addr>[,options]
- uart,mmio,<addr>[,options]
+ uart[8250],io,<addr>[,options]
+ uart[8250],mmio,<addr>[,options]
Start an early, polled-mode console on the 8250/16550
UART at the specified I/O port or MMIO address,
switching to the matching ttyS device later. The
options are the same as for ttyS, above.
+ earlycon= [KNL] Output early console device and options.
+ uart[8250],io,<addr>[,options]
+ uart[8250],mmio,<addr>[,options]
+ Start an early, polled-mode console on the 8250/16550
+ UART at the specified I/O port or MMIO address.
+ The options are the same as for ttyS, above.
+
cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Format:
<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]